1. Field of the Invention
This invention relates to an externally operated mechanism for a distribution transformer, and more particularly, it pertains to a pair of open-close load break switches for accomplishing three- or four-position feed conditions to a pad mounted distribution transformer.
2. Description of the Prior Art
In order to provide loop feed capability to pad mounted distribution transformers using simple open-close switches, the so-called "quick-make and quick break" type of switch is particularly suitable for the switch contacts immersed in transformer oil. Such switches are disclosed in U.S. Pat. Nos. 3,461,259 and 3,590,183 and are provided with an overcenter spring mechanism for rotatably moving contact structures for opening and closing circuits. The rotatable moving contact structure comprises a rotatable contact carriage carrying parts of contact fingers extending outwardly from the rotatable carriage and making separable engagement with corresponding stationary-spaced blade-shaped contacts.
Formerly, where a transformer was fed from either of two supply lines, such as lines A and B, two open-close switches were used to obtain four switch positions; namely, both switches open, both switches closed, one switch open and the other closed, and the one switch closed and the other open. Where, however, one line, such as line B, is converted to ground, it is necessary to switch between open, close, and ground positions, for which the conventional switch has been inoperative.
Accordingly, a need exists for a switch mechanism which is operable between four positions for a two line supply and three positions for a one line supply with the other line grounded.